Li Yan-Wei, Ciamarra Massimo Pica
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore.
CNR-SPIN, Dipartimento di Scienze Fisiche, Università di Napoli Federico II, I-80126, Napoli, Italy.
Phys Rev E. 2020 Dec;102(6-1):062101. doi: 10.1103/PhysRevE.102.062101.
The phase diagram of the prototypical two-dimensional Lennard-Jones (LJ) system, while extensively investigated, is still debated. In particular, there are controversial results in the literature with regard to the existence of the hexatic phase and the melting scenario. Here we study the phase behavior of two-dimensional range-limited LJ particles via large-scale numerical simulations. We demonstrate that at a high temperature, when the attraction in the potential plays a minor role, melting occurs via a continuous solid-hexatic transition followed by a first-order hexatic-fluid transition. The hexatic phase occurs in a density range that vanishes as the temperature decreases so that at low-temperature melting occurs via a first-order liquid-solid transition. The temperature where the hexatic phase disappears is well above the liquid-gas critical temperature. The evolution of the density of topological defects confirms this scenario.
典型二维 Lennard-Jones（LJ）系统的相图虽已得到广泛研究，但仍存在争议。特别是，文献中关于六次近晶相的存在以及熔化过程存在相互矛盾的结果。在此，我们通过大规模数值模拟研究二维有限范围 LJ 粒子的相行为。我们证明，在高温下，当势场中的吸引力作用较小时，熔化通过连续的固 - 六次近晶转变，随后是一级六次近晶 - 流体转变发生。六次近晶相出现在一个随温度降低而消失的密度范围内，因此在低温下熔化通过一级液 - 固转变发生。六次近晶相消失的温度远高于液 - 气临界温度。拓扑缺陷密度的演变证实了这一过程。
